1. Field of the Invention
The present invention relates to a thermal transfer recording device and more particularly to a thermal transfer recording device which enables full color recording with a single recording operation using a thermal head.
2. Description of the Related Art
Thermal transfer recording devices have been widely used where a plurality of heating elements in a thermal head are selectively activated and heated according to image data to transfer ink from the ink ribbon to a recording medium to record a desired image.
Recently, among these thermal transfer recording devices, line printers have been spreading due to the growing demand for compactness. In a line printer, a line thermal head whose length matches the recording media""s recording area width is pressed against a platen roller with the recording media and ink ribbon between them to perform recording.
This type of line printer uses an ink ribbon which bears cyan, magenta, and yellow inks successively in a cyclic pattern and transfers these color inks onto the recording medium in a way for them to overlap each other to record a full color image.
For full color image recording in this type of line printer, while the line thermal head is pressed against the platen roller with the recording medium and ink ribbon between them, a plurality of heating elements in the line thermal head are selectively heated according to image data and at the same time the platen roller is rotated to move the recording medium and the ink ribbon so that a first color ink is transferred from the ink ribbon to the recording medium to record the desired image on the medium.
After completion of recording with the first color ink, the line thermal head is separated from the platen roller, the paper feed roller is rotated in the reverse direction to move back the recording medium by a prescribed amount while the ink ribbon is not rewound.
Then, as in the above procedure, while the line thermal head is pressed against the platen roller with the recording medium and ink ribbon between them, the heating elements in the line thermal head are selectively heated and the recording medium and the ink ribbon are moved, so a desired image is printed on the recording medium. The above procedure takes place for each color ink of the ink ribbon so that a full color image is recorded on the recording medium.
However, the conventional thermal transfer recording device as mentioned above has the problem that because the procedure (recording operation) is repeated for each of cyan, magenta and yellow inks, it takes a considerable time to record a full color image. In other words, it is very low in recording efficiency.
In addition, since the recording operation has to be repeated for each color, power consumption is considerable. Recently, portable recording devices have been becoming popular. If this method should be used in a portable recording device, it would cause inconvenience in use because it consumes much battery power and cannot be used for a long time.
The present invention has been made in view of the above circumstances. One object of the present invention is to provide a thermal transfer recording device which enables full color recording with a single recording operation and thus increases the recording efficiency remarkably and reduces power consumption, and a method therefor.
Another object of the present invention is to provide a thermal transfer recording device having a thermal head for recording a desired image or the like on a recording medium, in which, while the thermal head or the recording medium is moving at a prescribed speed with the thermal head pressed against the recording medium with an ink ribbon bearing thermal transfer inks between them, heating elements in the thermal head are selectively activated according to image data to make them generate heat in order to record a desired image or the like. The recording device uses, as the recording medium, a heat-sensitive recording medium which colors when heated, and has control means to control electric energy supplied to the heating elements in the thermal head. Here, the control means control the electric energy supplied to the heating elements according to the image data in a way to bring its level into one of the following ranges: a white range in which the recording medium does not turn black and the thermal transfer inks of the ink ribbon are not transferred; a color range in which the recording medium does not turn black and the thermal transfer inks are transferred; or a black range in which the recording medium turns black.
In this case, the control means control the electric energy supplied to the thermal head to bring its level into the white, color or black range depending on image data to record a full color image and recording of a full color image is performed through a single recording operation. This remarkably increases the recording speed, remarkably improves the recording efficiency and reduces power consumption.
A further object of the present invention is to provide a thermal transfer recording device as mentioned above in which the thermal head is a line thermal head, and the ink ribbon includes successive lines of R, G, and B thermal transfer inks extending along a row of heating elements in the line thermal head.
According to the invention, when the thermal head is a line thermal head and the ink ribbon includes successive lines of R, G, and B thermal transfer inks extending along a row of heating elements in the line thermal head, a line printer capable of recording full color images is realized.